Project Summary The use of NPs in commercially available products is rapidly increasing. As their use becomes more widespread, human exposure will consequently increase. Due to NPs unique properties, the potential hazards of NPs are only now being identified. There is a growing need for systematic toxicity studies especially to the very special cell type-stem cells. However, information is very limited regarding how stem cells respond to NPs. Our previous studies indicated the carbon nanotube and nanosilver particles can induce a DNA damage response in mouse embryonic stem cells. Stem cells are a unique cell population with the ability to undergo both self-renewal and differentiation. Adult stem cells constantly provide new cell lineages in our body. Increasing amounts of evidence suggest that stem cells may be the sources of mutant cells that give rise to cancerous tumors and maintain tumor growth. The systemic and detailed characterization of both cytotoxic and genotoxic Microsoft Office Word 2007.lnk effects of manufactured NP exposure to both embryonic stem cells, induced stem cells (iPS) and adult stem cells will thoroughly evaluate the health and safety effects of NPs and greatly enhance consumer confidence. In this proposal, we will be initially using four NP types that are, or will be, prominently used in commercially available products: carbon NPs (car wax, fuel lines, cosmetics), silver NPs (antimicrobial wound dressings, odor-reducing socks), titanium dioxide NPs (sunscreens, paints), and zinc oxide NPs (sunscreens). It is vital to have confidence in the suppliers of these NPs. We are fortunate to have strong collaborative links with NP manufacturing experts within the University of Dayton and other institutes who will provide these particles. We propose the following specific aims: Aim 1. Characterize the impact of these selected manufactured nanoparticles to stem cells self renewal and differentiation potentials. Mouse embryonic stem cells, induced human pluripotent stem cells (ihPS), and human mesenchymal stem cells will be used for this study. Aim2. Investigate p53 activation as a possible molecular marker to study the stem cell cytotoxic and genotoxic response to these selected manufactured nanoparticles. Aim3. Using an endogenous molecular marker adenine phosphoribosyltransferase (Aprt) as a reporter to study genotoxic effect to these selected nanoparticles.